A database system is an organized body of related information. Typically, a database stores a variety of information for an entity. Frequently, a database has different clients that access it for different reasons. Some database users, for example, are interested in changes that occur in a database. A change in a database can be significant or minor and may be called an event. Normally, a database user is not interested in every event that occurs in a database. More likely, a database user is only interested in the occurrence of certain database events. As a consequence of this need, database notification infrastructures allow database users to set up event registrations in which the clients can receive event notifications when certain database events occur. For example, a user can set up an event registration so that an event notification will be sent when a event notification is being enqueued and the message may indicate that a database change has happened.
Traditionally, in order for a client to consume an event notification, the client must establish or maintain an active connection with the database and request the database for the event notification. Alternatively, a client may register with the database to be notified when an event notification becomes available. However, certain types of event notifications, such as an ADT event notification payload, cannot be delivered to the client unless the client has an active session with the database because the format is proprietary and requires the client to be connected to the database. In other words, an ADT formatted notification may not be read offline.
This approach may be problematic and may cause inefficiency. For example, a database and a client's geographical locations may cause it to be inconvenient or impossible for the client to frequently communicate with the database. As a result, clients will not be able to consume event notifications as efficiently. Also, databases may be required to devote more memory space into storing unconsumed event notifications.
Furthermore, conventionally, delivery of an event notification means the entire event notification is sent to the client. However, certain event notifications may be very large and a client may be only interested in a small portion of the event notification. For example, an event notification regarding an instance of a database going down may contain information such as what time the database went down, why the database went down, and thousands of bytes of other detailed information. However, a client may be only interested in what time the database went down and may not care about the remainder of the data.
Thus, delivering complete event notifications will often lead to a waste of resources. By delivering unnecessary information along with pertinent information, communication bandwidth and processing power of databases are diverted away from other applications. Consequently, the overall efficiency of databases will be lowered.